1. Technical Field
The present invention relates to a rotating storage device and a control method thereof, and more particularly relates to a control technique by which contamination in a hard disk unit or for a write error caused by contamination etc. and the negative effects resulting therefrom are reduced.
2. Description of the Related Art
If contamination such as dust exists in a hard disk unit, adhesion of contamination onto a read/write head may cause unstable flight of the head. Contamination adhered on a magnetic disk medium in the hard disk unit may also cause adhesion of the contamination onto the head or an error in information read/write on the magnetic disk.
Therefore, in processes of assembling the hard disk unit, anti-contamination measures, such as sufficient cleaning of parts, assembly in a clean environment (clean room, etc.), and adopting an automated processing by mechanization are taken. However, the nature of many hard disk assembly processes do not lend themselves to automation so that manual, dust-generating processes may not be eliminated. Also, insufficient cleaning of parts cannot be avoided because of unequal process capabilities. Consequently, a certain level of contamination shall inevitably occur.
Accordingly, the conventional art includes measures for various types of contamination or defects and growth of defects caused by contamination. For example, Japanese Patent (Laid-Open) No.2000-156051 discloses the art to judge that adjacent defect registration is required for a read error recoverable by offset read and perform the adjacent defect registration of a sector in the reverse direction of said sector and offset direction. Thus, the minimum defect can be registered before a defect grows by performing adjacent defect registration after detecting a read error, and high data reliability can be obtained with the minimum number of defective sectors.
As another example, Japanese Patent (Laid-Open) Heisei No.5-28675 discloses the art to use a magnetic head lift mechanism to make a magnetic head contact a magnetic disk immediately before the start of rotating the magnetic disk, then rotate the magnetic disk in this state. Said report indicates that minute dust can be removed by making the magnetic head contact the magnetic disk.
As a further example, Japanese Patent (Laid-Open) Heisei No.5-54577 discloses the art to stop or slow down rotation of the spindle while the magnetic head is not performing a read/write operation, then make the magnetic head contact the magnetic disk. The report says that minute dust can be removed by making the magnetic head contact the magnetic disk.
Japanese Patent (Laid-Open) Heisei No.6-203503 discloses the art to contrive loading and unloading periods focusing on changes in the tangential force of head contact to the contact start stop (CSS) in order to prevent the disk from being damaged and remove dust adhered on the head rail surface. Both prevention of a disk damage and dust removal are enabled by controlling load and unload operations to be performed while the number of disk rotations is few.
As a further example, Japanese Patent (Laid-Open) Heisei No.2000-90612 discloses the art to remove dust from a contact pad by controlling numbers of disk rotations at load and unload operations for controlling the pitch angle of the head slider to efficiently remove dust adhered and accumulated on the contact type head slider.
However, the recent improvement of storage density requires more detailed measures to defect on a disk surface and defect growth. Even levels of contamination and defects out of matter with conventional arts do matter with the hard disk unit enabling high storage density. All measures for the contamination provided by conventional arts are to make the head contact the magnetic disk medium, and are not appropriate for the hard disk unit of high storage density designed on premise of higher storage density. Contact between the head and disk may cause new contamination.
For the art described in above-described Japanese Patent (Laid-Open) Heisei No.2000-156051, a specific result can be expected for defect growth, but no measure is taken for an existing defect and only a passive measure such as not to use peripheral storage area assuming that they are defective sectors is taken.